1. Field of the Invention
The present invention relates to an endoscope in which an optical member is water-tightly fixed to a distal end portion of an insertion portion.
2. Description of the Related Art
An endoscope for observing inside of a body of a subject by an image pickup section disposed at a distal end portion and performing remedy/treatment using a treatment instrument projected from the distal end portion by inserting an elongated insertion portion into the body of the subject which cannot be observed from outside is widely used. The endoscope after use is disinfected and sterilized in order to prevent inter-patient infection via the endoscope.
As a disinfecting and sterilization method for an endoscope, an autoclave method (high-temperature and high-pressure steam method) becomes mainstream. In the autoclave method, any complicated operation is not required and the endoscope can be used immediately after sterilization and a running cost is low. However, in the autoclave method, since an entire endoscope is subjected to a high-temperature and high-pressure state, an O-ring or the like that water-tightly seals a lens of an image pickup optical system or the like disposed at the distal end portion and a lens frame for holding the lens, tends to deteriorate so that there is a fear that steam invades the optical system. Similarly, if the lens is fixed to the lens frame with adhesive composed of resin, there is a case where the steam invades a space inside the lens frame and the lens is fogged from inside.
In Japanese Patent Laid-Open Publication No. 2002-253487, an endoscope in which a lens is fixed to a lens frame by solder is disclosed. The above endoscope realizes water-tight seal with high reliability by using solder, which is a metal material, as a bonding member.
In Japanese Patent Laid-Open Publication No. 2004-82199, there is disclosed solder that can be bonded to an optical member composed of an oxide such as glass. By using the solder disclosed in the above publication, the lens can be fixed to the lens frame without forming a metal film for soldering on the lens.